Disconnectable driveline for all-wheel drive vehicle

ABSTRACT

A vehicle driveline that includes a differential assembly, a two-speed transmission, a power take-off unit, a range sleeve, a mode sleeve and an input shaft. The range sleeve is non-rotatably but axially slidably coupled to the input shaft. The range sleeve provides rotary power to the two-speed transmission and is movable into different positions to control the gear ratio in which the two-speed transmission operates. The two-speed transmission outputs rotary power to the differential assembly. The mode sleeve is selectively movable into a position where it transmits rotary power between the range sleeve and a PTU input of the power-take off unit. Movement of the range and mode sleeves can be coordinated to provide a two-wheel drive high speed mode, a four-wheel drive high speed mode and a four-wheel drive low speed mode.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/244,158 filed Apr. 3, 2014, which is a continuation of U.S. patentapplication Ser. No. 13/470,941 filed May 14, 2012 (now U.S. Pat. No.8,795,126 issued Aug. 5, 2014). The disclosure of each of theabove-referenced patent applications is incorporated by reference as iffully set forth in detail herein.

FIELD

The present disclosure relates generally to all-wheel drive vehicles andmore particularly to single-speed and multi-speed disconnectabledrivelines for all-wheel drive vehicles.

BACKGROUND

This section provides background information related to the presentdisclosure which is not necessarily prior art.

Many modern automotive vehicles, such as crossover vehicles, areavailable with an all-wheel drive (AWD) drivetrain that is based on afront-wheel drive (FWD) architecture. This optional drivetrainarrangement permits drive torque to be selectively and/or automaticallytransferred from the powertrain to both the primary (i.e., front)driveline and the secondary (i.e., rear) driveline to provide bettertraction when the vehicle is operated in inclement weather and onoff-highway road conditions. Such AWD vehicles necessarily are equippedwith a much more complex drivetrain which, in addition to the primarydriveline, must include the additional components associated with thesecondary driveline such as a power take-off unit and a propshaft.

In an effort to minimize driveline losses (i.e., viscous drag, friction,inertia and oil churning) associated with secondary driveline beingback-driven when no drive torque is transmitted thereto, it is known toincorporate a disconnect system that is configured to uncouplecomponents of the secondary driveline such as, for example, the rearwheels or the rear differential from the remainder of the secondarydriveline. To this end, there remains a need in the art for developmentof improved disconnectable drivelines for use in AWD vehicles.

SUMMARY

It is an aspect of the present teachings to provide a disconnectablesecondary driveline arrangement for use with all-wheel drive vehiclesthat includes a single-speed power take-off unit having a disconnectmechanism, a single-speed rear drive module having a torque transferdevice capable of providing a disconnect function, a speed synchronizingfunction and a torque biasing function, and a control system forcontrolling actuation of the disconnect mechanism and the torquetransfer device.

It is another aspect of the present teachings to provide adisconnectable secondary driveline arrangement for use with all-wheeldrive vehicles that includes a two-speed power take-off unit having adisconnect mechanism and range shift mechanism, a two-speed rear drivemodule having a torque transfer device and a range shift mechanism, anda control system for controlling coordinated actuation of the two-speedpower take-off unit and the two-speed rear drive module.

In accordance with these and other aspects of the present teachings, anall-wheel drive vehicle can include a powertrain, a primary driveline, apower switching mechanism, a secondary driveline, and a control system.The powertrain can include a prime mover and a transmission having anoutput. The primary driveline is driven by the transmission output andis operable to direct rotary power from the prime mover to a pair ofprimary vehicle wheels. The power switching mechanism is operable underthe control of the control system in one of a disconnected mode and aconnected mode. The power switching mechanism is operable in itsconnected mode to direct rotary power from the transmission output tothe secondary driveline. The secondary driveline can include a reardrive module and a propshaft that couples an output of the powerswitching mechanism to an input of the rear drive module. The rear drivemodule can include a secondary differential interconnecting a pair ofaxleshafts to a pair of secondary vehicle wheels, and a torque transferdevice operably disposed between the input and the secondarydifferential. The torque transfer device is operable under the controlof the control system in one of a disconnected mode and a connectedmode. The torque transfer device is operable in its connected mode todirect rotary power transmitted by the power switching mechanism to thesecondary differential. When the power switching mechanism and thetorque transfer device are in their disconnected modes, rotary power isonly transmitted to the primary vehicle wheels. The torque transferdevice is operable in its disconnected mode to prevent the secondaryvehicle wheels and the secondary differential from back-driving theinput of the rear drive module, the propshaft, and the output of thepower switching mechanism. The power switching mechanism is operable inits disconnected mode to prevent the transmission output from drivingthe output of the power switching mechanism and the propshaft.

In addition to the above, an all-wheel drive vehicle of the presentteachings can also include a two-speed power switching mechanism and atwo-speed rear drive module. The two-speed power switching mechanism isstill operable in its disconnected and connected modes but furtherincludes a planetary reduction mechanism and a range shift mechanismthat are operably disposed between the transmission output and a primarydifferential that drives the primary vehicle wheels. The power switchingmechanism is capable of establishing a two-wheel high-range driveconnection, a four-wheel high-range drive connection, and a four-wheellow-range drive connection between the transmission output and theprimary differential. The two-speed rear drive module is still operablein its disconnected and connected modes but further includes a planetaryreduction mechanism and a range shift mechanism that are operablydisposed between an output of the torque transfer device and thesecondary differential. The rear drive module is capable of establishinga high range drive connection and a low-range drive connection betweenthe output of the torque transfer device and an input to the secondarydifferential. The control system is operable to coordinate actuation ofthe two-speed power switching mechanism and the two-speed rear drivemodule.

In still another form, the present teachings provide a rear drive modulefor a drivetrain of an all-wheel drive motor vehicle. The rear drivemodule includes an axle housing, an input pinion rotatably coupled tothe axle housing, a spool rotatably coupled to the axle housing, a ringgear, a disconnect clutch, a differential assembly and a pair of axleshafts. The ring gear is coupled to the spool for rotation therewith andis meshingly engaged with the input pinion. The disconnect clutch has afirst clutch member, which is coupled to the spool for rotationtherewith, and a second clutch member. The disconnect clutch beingconfigured to selectively transmit rotary power between the first andsecond clutch members. The differential assembly has a differential caseand a differential gearset with a pair of differential outputs. Thedifferential gearset is configured to receive rotary power from thedifferential case and to output rotary power to the differentialoutputs. The hollow shaft is received in the spool and is coupled to thedifferential case for rotation therewith. The hollow shaft is configuredto transmit rotary power in a power path between the disconnect clutchand the differential assembly. Each axle shaft is coupled to acorresponding one of the differential outputs for rotation therewith.

In yet another form, the present disclosure provides a vehicle drivelinethat includes an input shaft, which is rotatable about a first axis, arange sleeve, a mode sleeve, a differential assembly, a two-speedtransmission and a power take-off unit. The range sleeve is concentricwith the input shaft and is non-rotatably but axially slidably coupledto the input shaft. The mode sleeve is concentric with the input shaft.The differential assembly has a differential case, which is rotatableabout the first axis, and a differential gearset. The two-speedtransmission receives rotary power from the range sleeve and outputsrotary power to the differential case. The power take-off unit has a PTUinput and a PTU output that is disposed along a second axis that is notparallel to the first axis. The two-speed transmission operates in afirst speed ratio when the range sleeve is positioned in a first rangesleeve position and in a second speed ratio when the range sleeve ispositioned in a second range sleeve position. The mode sleeve is movablebetween a first mode sleeve position, in which the mode sleeve isdisengaged from at least one of the PTU input member and the rangesleeve, and a second mode sleeve position in which the mode sleeve islocated in a position where it is capable of transmitting rotary powerbetween the range sleeve and the PTU input member. Movement of the rangesleeve and the mode sleeve is coordinated to provide a two-wheel drivehigh range operational mode, a four-wheel drive high range operationalmode and a four-wheel drive low range operational mode.

In still another form, the present disclosure provides a vehicledriveline that includes an input shaft, which is rotatable about a firstaxis, a range sleeve, a mode sleeve, a planetary transmission, adifferential assembly, an axle shaft and a power transfer unit. Therange sleeve is concentric with the input shaft and is non-rotatably butslidably coupled to the input shaft so as to be movable along the firstaxis between a first range sleeve position and a second range sleeveposition. The mode sleeve is concentric with the input shaft and isslidable along the first axis between a first mode sleeve position and asecond mode sleeve position. The planetary transmission has a planetcarrier, a sun gear and a plurality of planet gears that are rotatablymounted on the planet carrier and meshingly engaged to the sun gear. Thedifferential assembly has a differential case and a differentialgearset. The differential case is coupled to the planet carrier forcommon rotation about the first axis. The differential gearset isdisposed in the differential case and includes a pair of differentialoutput members. The axle shaft is coupled for rotation with one of thedifferential output members and extends through the sun gear and theinput shaft. The power transfer unit has a PTU input and a PTU outputthat is rotatable about a second axis that is transverse to the firstaxis. Placement of the range sleeve in the first range sleeve positioncouples the planet carrier to the input shaft for common rotation.Placement of the range sleeve in the second range sleeve positioncouples the sun gear to the input shaft for common rotation. Placementof the mode sleeve in the first mode sleeve position when the rangesleeve is in the first range sleeve position de-couples the range sleevefrom the PTU input to permit relative rotation between the range sleeveand the PTU input. Placement of the mode sleeve in the second modesleeve position when the range sleeve is in the first range sleeveposition couples the range sleeve to the PTU input for common rotation.

Further areas of applicability will become apparent from the descriptionand claims herein. The description and specific examples in this summaryare intended for purposes of illustration only and are not intended tolimit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only ofselected embodiments and are not intended to limit the scope of thepresent disclosure in any way. Similar or identical elements are givenconsistent reference numerals throughout the various figures.

The present disclosure will become more fully understood from thedetailed description and the accompanying drawings wherein:

FIG. 1 is a schematic of a motor vehicle equipped with a disconnectableall-wheel drive system constructed in accordance with the presentteachings;

FIG. 2 is a schematic illustration of a single-speed power take-off unitassociated with the disconnectable all-wheel drive system of FIG. 1;

FIG. 3 through FIG. 5 are perspective views of a single-speed powertake-off unit based on the schematic shown in FIG. 2 with its housingstructure removed for improved clarity and which is constructed inaccordance with the present teachings;

FIG. 6 is a sectional view of the single-speed power take-off unit takengenerally along line 6-6 of FIG. 5;

FIG. 7 is a schematic illustration of a single-speed rear drive moduleassociated with the disconnectable all-wheel drive system of FIG. 1;

FIGS. 8 through 10 are perspective views of a single-speed rear drivemodule based on the schematic shown in FIG. 7, with and without itshousing structure, and which is constructed in accordance with thepresent teachings;

FIG. 11 is a sectional view of the single-speed rear drive module takengenerally along line 11-11 of FIG. 10;

FIG. 12 is a schematic of a motor vehicle equipped with anotherconfiguration of a disconnectable all-wheel drive system constructed inaccordance with the present teachings;

FIG. 13 is a schematic illustration of a two-speed power take-off unitassociated with the disconnectable all-wheel drive system of FIG. 12;

FIG. 14 is an exploded perspective view of a two-speed power take-offunit based on the schematic shown in FIG. 13 and which is constructed inaccordance with the present teachings;

FIG. 15 is a sectional view of the two-speed power take-off unit shownin FIG. 14;

FIGS. 16A through 16D are partial sectional views of the two-speed powertake-off unit shown in FIG. 15 with its mode and range shift componentspositioned to define a two-wheel high-range (2-Hi) mode, a four-wheelhigh-range (4-Hi) mode, a neutral mode, and a four-wheel low-range(4-Low) mode, respectively;

FIGS. 17A through 17D are schematic illustrations of a two-speed reardrive module associated with the disconnectable all-wheel drive systemof FIG. 12 with its range shift components positioned to define ahigh-range (H) mode, a neutral (N) mode, a low-range (L) mode, and alow-range locked (LOCK) mode, respectively;

FIGS. 18 through 21 are perspective views of a two-speed rear drivemodule based on the schematics shown in FIGS. 17a through 17d , with andwithout its housing structure, and which is constructed in accordancewith the present teachings;

FIG. 22 is a sectional view taken generally along line 22-22 of FIG. 21;and

FIG. 23 is a partial sectional view of an alternative exemplaryembodiment of a two-speed rear drive module configured for use with thedisconnectable all-wheel drive system of FIG. 12.

DETAILED DESCRIPTION

The following exemplary embodiments are provided so that the presentdisclosure will be thorough and fully convey the scope to those skilledin the art. Numerous specific details are set forth such as examples ofspecific components, devices and schematic configurations to provide athorough understanding of exemplary embodiments of the presentdisclosure. However, it will be apparent to those skilled in the artthat these specific details need not be employed, that the exemplaryembodiments may be embodied in many different forms, and that neithershould be construed to limit the scope of the present disclosure.

With reference to FIG. 1 of the drawings, a motor vehicle constructed inaccordance with the teachings of the present disclosure is schematicallyshown and generally indicated by reference numeral 10. The vehicle 10can include a powertrain 12 and a drivetrain 14 that can include aprimary driveline 16, a power switching mechanism 18, a secondarydriveline 20, and a control system 22. In the various aspects of thepresent teachings, the primary driveline 16 can be a front drivelinewhile the secondary driveline 20 can be a rear driveline.

The powertrain 12 can include a prime mover 24, such as an internalcombustion engine or an electric motor, and a transmission 26 which canbe any type of ratio-changing mechanism, such as a manual, automatic, orcontinuously variable transmission. The prime mover 24 is operable toprovide rotary power to the primary driveline 16 and the power transfermechanism 18.

With additional reference to FIG. 2, the primary driveline 16 caninclude a primary or first differential 30 having an input member 32driven by an output member (not shown) of the transmission 26. In theparticular construction shown, the first differential 30 is configuredas part of the transmission 26, a type commonly referred to as atransaxle and typically used in front-wheel drive vehicles. The primarydriveline 16 can further include a pair of first axleshafts 34L, 34Rthat can couple output components of the first differential 30 to a setof first vehicle wheels 36L, 36R. The first differential 30 can includea first differential case 38 that is rotatably driven by the inputmember 32, at least one pair of first pinion gears 40 rotatably drivenby the first differential case 38, and a pair of first side gears 42meshed with the first pinion gears 40 and which are connected to drivethe first axleshafts 34L, 34R.

With continued reference to FIG. 2, the power switching mechanism 18,hereinafter referred to as a power take-off unit (PTU), can generallyinclude a housing 46, an input 48 coupled for common rotation with thefirst differential case 38 of the first differential 30, an output 50, atransfer gear assembly 52, a disconnect mechanism 54, and a disconnectactuator 56. The input 48 can include a tubular input shaft 58 rotatablysupported by the housing 46 and which concentrically surrounds a portionof the first axleshaft 34R. A first end of the input shaft 58 can becoupled for rotation with the first differential case 38. The output 50can include an output pinion shaft 60 rotatably supported by the housing46 and having a pinion gear 62. The transfer gear assembly 52 caninclude a hollow transfer shaft 64, a helical gearset 66, and a hypoidgear 68 that is meshed with the pinion gear 62. The transfer shaft 64concentrically surrounds a portion of the first axleshaft 34R and isrotatably supported by the housing 46. The helical gearset 66 caninclude a first helical gear 70 fixed for rotation with the transfershaft 64 and a second helical gear 72 which is meshed with the firsthelical gear 70. The second helical gear 72 and the hypoid gear 68 areintegrally formed on, or fixed for common rotation with, a stub shaft 74that is rotatably supported in the housing 46.

The disconnect mechanism 54 can comprise any type of clutch, disconnector coupling device that can be employed to selectively transmit rotarypower from the powertrain 14 to the secondary driveline 20. In theparticular example provided, the disconnect mechanism 54 is configuredas a dog clutch. The dog clutch can include a set of external splineteeth 76 formed on a second end of the input shaft 58, a set of externalclutch teeth 78 formed on the transfer shaft 64, a mode collar 80 havinginternal spline teeth 82 constantly meshed with the external splineteeth 76 on the input shaft 58, and a shift fork 84 operable to axiallytranslate the shift collar 80 between a first mode position and a secondmode position. While schematically shown as a non-synchronized dogclutch, it will be understood that the disconnect mechanism 54 caninclude a synchronized dog clutch if such a configuration is desired.

The mode collar 80 is shown in its first mode position, identified by a“2WD” leadline, wherein the internal spline teeth 82 on the mode collar80 are disengaged from the external clutch teeth 78 on the transfershaft 64. As such, the input shaft 58 is disconnected from drivenengagement with the transfer shaft 64. Thus, no rotary power istransmitted from the powertrain 12 to the transfer gear assembly 52 andthe output pinion shaft 60 of the power take-off unit 18. With the modecollar 80 in its second mode position, identified by an “AWD” leadline,its internal spline teeth 82 are engaged with both the external splineteeth 76 on the input shaft 58 and the external clutch teeth 78 on thetransfer shaft 64. Accordingly, the mode collar 80 establishes a driveconnection between the input shaft 58 and the transfer shaft 64 suchthat rotary power from the powertrain 12 is transmitted through thepower take-off unit 18 to the output pinion shaft 60. As will bedetailed, the output pinion shaft 60 is coupled via a propshaft 86 tothe secondary driveline 20.

The disconnect actuator 56 can be any type of actuator mechanism that isoperable for axially moving the shift fork 84 which, in turn, causesconcurrent axial translation of the mode collar 80 between its twodistinct mode positions. The disconnect actuator 56 is shown mounted tothe housing 46 of the power take-off unit 18. The disconnect actuator 56can be a power-operated mechanism that can receive control signals fromthe control system 22 and can include, for example,hydraulically-actuated, pneumatically-actuated orelectromechanically-actuated arrangements.

As noted, FIG. 2 schematically illustrates the components that can beassociated with the power take-off unit 18. Reference now to FIG. 3through 6 will provide a more definitive structural configuration ofsuch components that are associated with an exemplary embodiment of thepower take-off unit 18. In particular, these figures illustrate thecomponents in an assembled condition with the housing 46 removed forimproved clarity. Each of the input shaft 58, the transfer shaft 64, thestub shaft 74, and the output pinion shaft 60 are shown with suitablebearings assembled thereon for rotatably supporting each within or fromthe housing 46. The disconnect actuator 56 is shown as a self-containedpower-operated unit 88 from which the shift fork 84 extends. Thepower-operated unit 88 can include an electric motor and a geared driveunit configured to convert rotation of the motor output intotranslational movement of the shift fork 84. External spline teeth 90are provided on one end of the first axleshaft 34R for facilitating asplined connection with its respective first side gear 42 in the firstdifferential 30. Likewise, external spline teeth 92 are provided on thefirst end of the input shaft 58 for facilitating a splined connectionwith a mating portion of the first differential case 38.

With particular reference now to FIGS. 1 and 7, the secondary driveline20 can include the propshaft 86, a rear drive module (RDM) 100, a pairof second axleshafts 102L, 102R, and a set of second vehicle wheels104L, 104R. A first end of the propshaft 86 can be coupled for rotationwith the output pinion shaft 60 extending from the power take-off unit18 while a second end of the propshaft 86 can be coupled for rotationwith an input 106 of the rear drive module 100. The rear drive module100 can include a housing 108, a secondary or second differential 110, atorque transfer device (TTD) 112 that is generally configured andarranged to selectively couple and transmit rotary power from the input106 to the second differential 110, and a TTD actuator 114. The input106 can include an input pinion shaft 116 having a pinion gear 118, ahollow spool 120, and a hypoid gear 122 fixed for rotation with thespool 120 and which is meshed with the pinion gear 118. The seconddifferential 110 can include a second differential case 124, at leastone pair of second pinion gears 126 rotatably driven by the seconddifferential case 124, and a pair of second output side gears 128 thatare meshed with the second pinion gears 126. The second output sidegears 128 are fixed for rotation with the inboard ends of the secondaxleshafts 102L, 102R.

The torque transfer device 112 can include any type of clutch orcoupling device that can be employed to selectively transmit rotarypower from the input 106 to the second differential 110. In the exampleshown, the torque transfer device 112 is a multi-plate friction clutchthat can include an input clutch member 130 driven by the spool 120, anoutput clutch member 132 coupled for rotation with the seconddifferential case 124, a multi-plate clutch pack 134 having interleavedfriction plates disposed between the input and output clutch members,and an engagement member 136 that is moveable for selectively applying aclutch engagement force to the clutch pack 134. An elongated hollowclutch output shaft 138 can connect the output clutch member 132 forcommon rotation with the second differential case 124 and is configuredto surround a portion of the second axleshaft 102R. The TTD actuator 114is provided to generate translational movement of the engagement member136 relative to the clutch pack 134 and can be controlled by controlsignals from the control system 22.

A first or “disconnected” mode can be established for the torquetransfer device 112 when the engagement member 136 is positioned suchthat rotary power is not transmitted from the input clutch member 130 tothe output clutch member 132. In this “disconnected” mode, the secondvehicle wheels 104L, 104R, the second axleshafts 102L, 102R, the seconddifferential 110, the clutch output shaft 138 and the output clutchmember 132 are disconnected from the input 106 of the rear drive module100. As such, rotation of these components as a result of rolling motionof the second vehicle wheels does not “back-drive” the propshaft 86 andcomponents of the power take-off unit 18.

A second or “connected” mode for the torque transfer device 112 can beestablished when the clutch engagement force exerted by the engagementmember 136 on the clutch pack 134 causes rotary power to be transmittedfrom the input 106 to the clutch output shaft 138 for delivery to therear wheels 104L, 104R through the second differential 110. In addition,a “torque biasing” function can also be provided in the connected modesince variable control over the magnitude of the clutch engagement forceapplied to the clutch pack 134 can vary the distribution ratio of therotary power transmitted from the powertrain 12 to the primary driveline16 and the secondary driveline 20. Thus, the torque transfer device 112can be configured or controlled to slip or cyclically engage anddisengage as appropriate for biasing the available drive torque whileestablishing the drive connection between the input 106 and the seconddifferential 110.

The TTD actuator 114 can be any power-operated device capable ofshifting the torque transfer device 112 between its first and secondmodes as well as adaptively regulating the magnitude of the clutchengagement force exerted by the engagement member 136 on the clutch pack134. Thus, the TTD actuator 114 can, for example, include anelectromagnetic or motor-driven ballscrew, ballramp or other camactuation system having a mechanical connection, shown by lead line 140,with the engagement member 136. Alternatively, the TTD actuator 114 caninclude a hydraulic actuation system capable of regulating the positionof the engagement member 136 relative to the clutch pack 134 byregulating fluid pressure, also indicated by lead line 140, delivered toa pressure chamber.

The control system 22 is schematically shown in FIG. 1 to include acontroller 150, a group of first sensors 152, and a group of secondsensors 154. The group of first sensors 152 can be arranged within themotor vehicle 10 to sense a vehicle parameter and responsively generatea first sensor signal. The vehicle parameter can be associated with anycombination of the following: vehicle speed, yaw rate, steering angle,engine torque, wheel speeds, shaft speeds, lateral acceleration,longitudinal acceleration, throttle position and gear position withoutlimitations thereto. The group of second sensors 154 can be configuredto sense a driver-initiated input to one or more on-board devices and/orsystems within the vehicle 10 and responsively generate a second sensorsignal. For example, the motor vehicle 10 may be equipped with a sensorassociated with a mode selection device, such as a switch associatedwith a push button or a lever, that senses when the vehicle operator hasselected between vehicle operation in a two-wheel drive (FWD) mode andan all-wheel drive (AWD) mode. Also, switched actuation of vehicularsystems such as the windshield wipers, the defroster, and/or the heatingsystem, for example, may be used by the controller 150 to assess whetherthe motor vehicle 10 should be shifted automatically between the FWD andAWD modes.

As noted, FIG. 7 schematically illustrates the components that can beassociated with the rear drive module 100. Referring now to FIGS. 8through 11, a more definitive structural configuration of suchcomponents associated with an exemplary embodiment of the rear drivemodule 100 is shown. These views illustrate the components in anassembled condition, with and without the housing 108. Each of the inputpinion shaft 116, the second axleshafts 102L and 102R, the seconddifferential case 124, the spool 120 and the clutch output shaft 138 areshown with suitable bearings assembled thereon for rotatably supportingeach within or from the housing 108. In addition, FIG. 11 specificallyshows that the spool 120 is fixed for rotation via a splined connection156 with an annular sleeve portion 158 of a clutch hub 160 which definesthe input clutch member 130. Likewise, the output clutch member 132 canbe a clutch drum 162 that is coupled via a splined connection 164 forrotation with a first end of the clutch output shaft 138. The oppositeend of the clutch output shaft 138 is fixed via a splined connection 166to a tubular boss portion 168 of the second differential case 124. Theengagement member 136 can be an apply piston disposed in the pressurechamber which is supplied with pressurized hydraulic fluid by ahydraulically-operated unit 169 associated with the TTD actuator 114.The hydraulically-operated unit 169 can include a motor-driven fluidpump 170, an accumulator 172 and related hydraulic components, all ofwhich are disposed in close proximity to or attached to the housing 108.

With reference to FIGS. 1, 2 and 7, the vehicle 10 can normally beoperated in the two-wheel drive (FWD) mode in which the power take-offunit 18 and the rear drive module 100 are both disengaged. Specifically,the mode collar 80 of the disconnect mechanism 54 is positioned by thedisconnect actuator 56 in its first (2WD) mode position such that theinput shaft 58 is uncoupled from the transfer shaft 64. As such,substantially all power provided by the powertrain 12 is transmitted tothe primary driveline 16. Likewise, the torque transfer device 112 canbe shifted into and maintained in its first (disconnected) mode suchthat the input 106, the propshaft 86, the output pinion shaft 60 and thetransfer gear assembly 52 within the power take-off unit 18 are notback-driven due to rolling movement of the second vehicle wheels 104.

When it is desired or necessary to operate the motor vehicle 10 in theall-wheel drive (AWD) mode, the control system 22 can be activated via asuitable input which, as noted, can include a drive requested input (viathe mode select device) and/or an input generated by the controller 150in response to signals from the first sensors 152 and/or the secondsensors 154. The controller 150 initially signals the TTD actuator 114to shift the torque transfer device 112 into its second (connected)mode. Specifically, the controller 150 controls operation of the TTDactuator 114 such that the actuation member 136 is moved and a clutchengagement force is exerted on the clutch pack 134 that is sufficient tosynchronize the speed of the secondary driveline 20 with the speed ofthe primary driveline 16. Upon speed synchronization, the controller 150signals the actuator 56 to cause the mode collar 80 in the powertake-off unit 18 to move from its first mode position into its secondmode position. With the mode collar 80 in its second mode position,rotary power is transmitted from the powertrain 12 to the primarydriveline 16 and the secondary driveline 20. It will be appreciated thatsubsequent control of the magnitude of the clutch engagement forcegenerated by the torque transfer device 112 permits torque biasingacross the clutch pack 134 for controlling the torque distribution ratiotransmitted from the powertrain 12 to the primary driveline 16 and thesecondary driveline 20.

With reference to FIG. 12, another motor vehicle constructed inaccordance with the present teachings is generally indicated byreference numeral 10′. The vehicle 10′ is generally similar to thevehicle 10 of FIG. 1 except that the primary driveline 16′ and thesecondary driveline 20′ have been modified to incorporate a two-speedrange unit into both the power take-off unit 18′ and the rear drivemodule 100′. As will be detailed, this alternative drivetrainarrangement for the vehicle 10′ permits establishment of at least oneall-wheel low range drive mode in addition to the two-wheel high-rangedrive mode and the all-wheel high-range drive mode associated withvehicle 10. For purposes of clarity, primed reference numeral are usedto designate components that are generally similar in structure and/orfunction to the non-primed components previously described in relationto FIGS. 1 through 11.

With additional reference now to FIG. 13, the power take-off unit 18′ isgenerally shown to include a housing 46′, an input 48′ adapted forconnection to an output member of the transmission 26′, an output 50′, atransfer gear assembly 52′, a first differential 30′, a disconnectmechanism 54′, a two-speed range unit 198, and a disconnect actuator56′. The input 48′ can include a hollow input shaft 204 rotatablysupported by the housing 46′ and surrounding the axleshaft 34L′. Theoutput 50′ can include an output pinion shaft 60′ having a pinion gear62′. The transfer gear assembly 52′ can include a hollow transfer shaft64′, a helical gearset 66′, and a hypoid gear 68′ meshed with the piniongear 62′. The helical gearset 66′ can include a first helical gear 70′fixed for rotation with the transfer shaft 64′ and a second helical gear72′ that is meshed with the first helical gear 70′. The second helicalgear 72′ and the hypoid gear 68′ are integral with or fixed to a stubshaft 74′ that is rotatably supported by the housing 46′.

The two-speed range unit 198 can include a planetary gear assembly 200and a range shift mechanism 202. The planetary gear assembly 200 caninclude a ring gear 206 non-rotatably fixed to the housing 46′, a sungear 208, a plurality of planet gears 210 meshed with both the ring gear206 and the sun gear 208, and a planet carrier 212 from which the planetgears 210 are rotatably supported. The planet carrier 212 is fixed to,or integrally formed with, the first differential case 38′ of the firstdifferential 30′ for common rotation therewith.

The range shift mechanism 202 can include a sun gear shaft 220surrounding a portion of the first axleshaft 34L′ and which is fixed forrotation with the sun gear 208, a carrier shaft 222 surrounding aportion of the sun gear shaft 220 and which is fixed for rotation withthe planet carrier 212, and a tubular range sleeve 224 surroundingportions of the carrier shaft 222, the sun gear shaft 220 and the inputshaft 204. The input shaft 204 can have a first end 226 adapted forconnection via a splined coupling shaft 227 (FIG. 14) to the output oftransmission 26′ and a second end having a set of elongated externalspline teeth 228 formed thereon. The range sleeve 224 can include a setof internal spline teeth 230 that are in continuous meshed engagementwith the external spline teeth 228 on the input shaft 204. As such, therange sleeve 224 is coupled for common rotation with the input shaft 204while being capable of bi-directional axial sliding movement thereonbetween a plurality of predefined range position which will be discussedhereinafter in greater detail. The range sleeve 224 further defines aset of internal clutch teeth 232 that can be moved into and out ofengagement with a set of external clutch teeth 234 formed on the carriershaft 222 or a set of external clutch teeth 236 formed on the sun gearshaft 220.

The disconnect mechanism 54′ is generally similar in function to thedisconnect mechanism 54 in that it is configured to selectively connectthe input shaft 204 to the transfer gear assembly 52′ for transmittingrotary power from the input shaft 204 to the output pinion shaft 60′when the all-wheel drive mode is desired. However, the disconnectmechanism 54′ differs in that the drive connection between the inputshaft 204 and the transfer shaft 64′ is made indirectly via the rangesleeve 224. In particular, the range sleeve 224 can include first andsecond sets of external spline teeth 240 and 242, respectively, whichare selectably engageable with internal spline teeth 244 formed on amode collar 246. As such, the mode collar 246 can be coupled forrotation with the range sleeve 224 and is capable of bi-directionalaxial translation relative to the range sleeve 224 between a first (2WD)mode position and a second (AWD) mode position.

In the first mode position, a set of internal clutch teeth 248 formed onthe mode collar 246 are released from meshed engagement with theexternal clutch teeth 78′ on the transfer shaft 64′, whereby no rotarypower is transmitted from the input shaft 204 through the transfer gearassembly 52′ to the output pinion shaft 60′. In contrast, with the modecollar 246 in its second mode position, its internal spline teeth 244are engaged with one of the first and second sets of external splines240 and 242 (depending on the axial position of the range sleeve 224)and its internal clutch teeth 248 are engaged with the clutch teeth 78′on the transfer shaft 64′, thereby establishing a drive connectionbetween the input shaft 204 and the output pinion shaft 60′.

The two-speed range unit 198 is operable to establish at least twodifferent speed ratio drive connections between the input shaft 204 andthe first differential 30′. Specifically, the range sleeve 224 can beaxially translated between a plurality of predefined range positions. Ina first or “high” (Hi) range position, the range sleeve 224 is locatedsuch that its internal clutch teeth 232 are engaged with the externalclutch teeth 234 on the carrier shaft 222. Since the internal splines230 on the range sleeve 224 remain in constant meshed engagement withthe external spline teeth 228 on the input shaft 204, location of therange sleeve 224 in its high-range position results in establishing adirect drive connection between the input shaft 204 and the carriershaft 222 which, in turn, is connected via the carrier 212 to the firstdifferential case 38′. As such, a first or direct ratio drive connectionis established between the input shaft 204 and the first differential30′.

In a second or “neutral” range position, the range sleeve 224 isdisconnected from driven connection with both of the carrier shaft 222and the sun gear shaft 220 such that the input shaft 204 is disconnectfrom the first differential 30′.

In a third or “low” (Low) range position, the range sleeve 224 islocated such that its internal clutch teeth 232 are engaged with theexternal clutch teeth 236 formed on the sun gear shaft 220. With therange sleeve 224 located in its low-range position, a second orreduced-ratio drive connection is established between the input shaft204 and the first differential 30′. Specifically, driven rotation of thesun gear shaft 220 causes the planetary gear assembly 200 to drive thecarrier 212 at a reduced speed relative to the input shaft 204 such thatthe primary driveline 16′ is likewise driven at the reduced speed ratiovia the first differential 30′.

With continued reference to FIG. 13, the disconnect actuator 56′ isshown positioned adjacent to the housing 46′ and can include a firstshift fork 84′ engaging the mode collar 246, a second shift fork 250engaging the range sleeve 224, and a power-operated unit 252 configuredto receive control signals from the controller 150 and operable tocoordinate movement of the shift forks 84′ and 250. The power-operatedunit 252 can be any type of unit capable of selectively translating thefirst shift fork 84′ for causing movement of the mode collar 246 betweenits two mode positions while also selectively translating the secondshift fork 250 for causing movement of the range sleeve 224 between itsthree range positions.

With reference now to FIGS. 14 and 15, a more definitive structuralconfiguration of the components associated with the two-speed powertake-off unit 18′ is shown. In particular, FIG. 14 illustrates anexploded perspective view of an exemplary embodiment of the two-speedpower take-off unit 18′. Housing 46′ is shown to include a multi-pieceassembly having a main housing 258 to which a differential housing 260and a PTU housing 262 are secured. FIG. 15 is a sectional view whichillustrates the compact arrangement of the planetary gear assembly 200,the range shift mechanism 202, the transfer gear assembly 52′, and themoveable mode collar 246 and range sleeve 224.

As will be understood, the bi-directional translational movement of therange sleeve 224 and the mode collar 246 can be coordinated to establisha plurality of mode and range combinations for the two-speed powertake-off unit 18′ based on control signals from the controller 150.Referring to FIGS. 16A through 16D, these various mode and rangecombinations can be more clearly illustrated.

FIG. 16A shows the positions of the range sleeve 224 and the mode collar246 for establishing a two-wheel high-range (2-Hi) mode. Specifically,the mode collar 246 is shown located in its first mode position whilethe range sleeve 224 is located in its first range position. As such,the input shaft 204 is coupled via the range sleeve 224 to the carriershaft 222 for establishing the direct drive connection between thepowertrain 12 and the primary driveline 16′. Concurrently, the transfershaft 64′ is disconnected from driven connection with the input shaft204, thereby disconnecting the secondary driveline 20′ from thepowertrain 12. Thus, rotary power is only transmitted by the powertrain12 to the primary driveline 16′ without speed reduction.

FIG. 16B shows the positions of the range sleeve 224 and the mode collar246 for establishing a four-wheel high-range (4-Hi) mode. Specifically,the high-range connection is maintained by the range sleeve 224remaining in its first range position while the mode collar 246 is shownmoved into its second mode position. Thus, the mode collar 246establishes a drive connection from the input shaft 204 (through therange sleeve 224) to the transfer shaft 64′ for also transmitting rotarypower from the powertrain 12 to the secondary driveline 20′ withoutspeed reduction.

FIG. 16C shows the positions of the range sleeve 224 and the mode collar246 for establishing a Neutral non-driven mode. As seen, the mode collar246 is maintained in its second mode position while the range sleeve 224has been axially moved into its second range position such that itsinternal splines 232 are disengaged from the external clutch teeth 234on the carrier shaft 220 and the external clutch teeth 236 on the sungear shaft 220. Thus, the input shaft 204 is disconnected from bothinputs to the primary driveline 16′ such that no rotary power istransmitted from the powertrain 12 to the primary driveline 16′. It willalso be noted that such movement of the range sleeve 224 to its secondrange position causes the internal spline teeth 244 on the mode collar246 to disengage the first set of external splines 240 on the rangesleeve 224 while the mode collar 246 maintains its connection with thetransfer gear 64′.

FIG. 16D shows the position of the mode collar 246 and the range sleeve224 for establishing a four-wheel low-range (4-Low) mode. Specifically,the mode collar 246 is maintained in its second mode position while therange sleeve 224 is moved axially into its third range position. Assuch, the low-range drive connection is established by the range sleeve224 between the input shaft 204 and the sun gear shaft 220 while the AWDconnection is established by the mode collar 246. It will be noted thatthe internal spline teeth 244 of the mode collar 246 engage the secondset of external spline teeth 242 upon movement of the range sleeve 224from its neutral range position into its low range position. While it ispossible to provide the external splines 240 and 242 on the range sleeve224 in a continuous arrangement, the non-toothed separation spacetherebetween has been recognized to inhibit potential tooth blockingconditions upon movement of the range sleeve 224 between its high-rangeand low-range positions.

With particular reference now to FIGS. 12 and 17, the secondarydriveline 16′ can include the propshaft 86, a two-speed rear drivemodule 10′, a pair of second axleshafts 102L′ and 102R′, and the set ofsecond vehicle wheels 104L and 104R. A first end of the propshaft 86 iscoupled to the output pinion shaft 60′ extending from the two-speedpower take-off unit 18′ while a second end of the propshaft 86 iscoupled for rotation with an input 106′ of the two-speed rear drivemodule 100′. The rear drive module 100′ can include a housing 108′, asecond differential 110′, a torque transfer device 112′ generallyconfigured and arranged to selectively couple and transmit rotary powerfrom the input 106′ to the second differential 110′, a TTD actuator 114′for controlling actuation of the torque transfer device 112′, atwo-speed range unit 278 having a planetary gear assembly 280 and arange shift mechanism 282, and a range actuator 284.

The input 106′ can include an input pinion shaft 116′ having a piniongear 118′, a hollow spool 120′, and a hypoid gear 122′ fixed to thespool 120′ and which is meshed with the pinion gear 118′. The seconddifferential 110′ includes a second differential case 124′, at least onepair of second pinion gears 126′ rotatably supported by the seconddifferential case 124′, and a pair of second output side gears 128′ thatare meshed with the second pinion gears 126′. The second output sidegears 128′ are fixed for rotation with the inboard ends of the secondaxleshafts 102L′ and 102R′.

Torque transfer device 112′ is generally similar to torque transferdevice 112 and can include an input clutch member 130′, an output clutchmember 132′, a clutch pack 134′, and an engagement member 136′ that ismoveable under the control of the TTD actuator 114′ based on controlsignals from the controller 150. The output clutch member 132′ can be aclutch drum 162′ that is coupled for rotation with a clutch output shaft286. Thus, torque transferred from the input 106′ through the torquetransfer device 112′ is transmitted to the clutch output shaft 286.

The two-speed range unit 278 is operable to establish at least twodifferent speed ratio drive connections between the output clutch member132′ and the second differential 110′. Specifically, the planetary gearassembly 280 can include a sun gear 290 fixed for rotation with theclutch output shaft 286, a ring gear 292 non-rotatably fixed to thehousing 108′, a plurality of planet gears 294 meshed with the sun gear290 and the ring gear 292, and a planet carrier 296 from which theplanet gears 294 are rotatably supported. The range shift mechanism 282can include a first or direct clutch ring 300 fixed for rotation withthe clutch output shaft 286, a second or low clutch ring 302 fixed forrotation with the planet carrier 296, a third or drive clutch ring 304fixed for rotation with a differential input shaft 306, a fourth or lockclutch ring 308 fixed for rotation with the second axleshaft 102R′, anda range sleeve 310. The differential input shaft 306 can surround thesecond axleshaft 102R′ and is connected for rotation with the seconddifferential case 124′ of the second differential 110′.

The range sleeve 310 can include a set of internal spline teeth 312 thatare in continuous meshed engagement with a set of external spline teeth314 formed on the drive clutch ring 304. As such, the range sleeve 310is coupled for common rotation with the drive clutch ring 304 whilebeing capable of bi-directional axial sliding movement thereon. Therange sleeve 310 further includes a set of internal clutch teeth 316. Aswill be detailed, translational movement of the range sleeve 310 isoperable to establish the two different speed range drive connectionsbetween the output shaft 286 of the torque transfer device 112′ and thesecond differential case 124′ of the second differential 110′.

The range sleeve 310 is shown in FIG. 17A positioned in a first or highrange position such that its internal spline teeth 312 are meshed withboth the external spline teeth 314 on the drive clutch ring 304 and witha set of external spline teeth 318 formed on the direct clutch ring 300.It will also be seen that the clutch teeth 316 on the range sleeve 310are disengaged from meshed engagement with a set of external clutchteeth 320 formed on the low clutch ring 302. Thus, a first or directratio drive connection is established between the output clutch member132′ and the second differential case 124′ of the second differential110′ via the clutch output shaft 286, the range sleeve 310 and thedifferential input shaft 306.

The range sleeve 310 is shown in FIG. 17B positioned in a second orneutral position such that its internal teeth 312 remain engaged onlywith the external teeth 314 on the drive clutch ring 304 while itsinternal clutch teeth 316 remain disengaged from the external clutchteeth 320 on the low clutch ring 302. As such, the output clutch member132′ is released from driven connection with the second differentialcase 124′ of the second differential 110′.

The range sleeve 310 is shown in FIG. 17C positioned in a third or lowrange position such that its internal spline teeth 312 remain meshedwith the external spline teeth 314 on the drive clutch ring 304 whileits internal clutch teeth 316 are now meshed with the external clutchteeth 318 on the low clutch ring 302. As such, driven rotation of thesun gear 290 (via the clutch output shaft 286) causes the planet carrier296 to rotate at a reduced speed to establish a second or reduced ratiodrive connection between the output clutch member 132′ and thedifferential case 124′ via the carrier 296, the low clutch ring 302, therange sleeve 310, the drive clutch ring 304, and the second differentialinput shaft 306.

Finally, FIG. 17D shows the range sleeve 310 positioned in a fourth orlow locked position. In this position, the internal spline teeth 312 onthe range sleeve 310 are meshed with both the external spline teeth 314on the drive clutch ring 304 and a set of external spline teeth 322formed on the lock clutch ring 308 while the internal clutch teeth 316on the range sleeve 310 remain engaged with the external clutch teeth320 on the low clutch ring 302. In this position, the reduced ratiodrive connection of FIG. 17C is maintained with the addition that thesecond differential 110′ is now locked since the second differentialcase 124′ and the second axleshaft 102R are prevented from rotatingrelative to each other.

With continued reference to FIGS. 17A through 17D, the range actuator284 can be any type of power-operated mechanism that is operable tocontrol axial translational movement of a range fork 324 which, in turn,causes movement of the range sleeve 310 between its four distinct rangepositions. The range actuator 284 is shown mounted to housing 108′ ofthe two-speed rear drive module 100′. The range actuator 284 ispreferably a motor-driven geared device configured to receive controlsignals from the controller 150 to convert rotation of the motor outputinto translational movement of the range fork 324.

As noted, FIGS. 17A through 17D schematically illustrate the componentsthat can be associated with the two-speed rear drive module 100′.Reference now to FIGS. 18-22 will provide a more definitive structuralconfiguration of such components that are associated with an exemplaryembodiment of the two-speed rear drive module 100′. In particular, asplined connection 330 is provided to couple the clutch drum 162′ to afirst end of the clutch output shaft 286. It is also shown that the sungear 290 can be formed integrally with the clutch output shaft 286.

With reference to FIG. 23, a partial sectional view of an alternativeexemplary embodiment of the two-speed rear drive module 100′ is shownwhich incorporates a modified range shaft mechanism 282′. In essence,the range shift mechanism 282′ is substantially similar to the rangeshift mechanism 282 shown in FIGS. 17A-22 with the exception that thelow lock clutch ring 308 has been eliminated to thereby eliminate thelow locked range mode shown in FIG. 17D. Thus, the range sleeve 310′ maybe slightly modified in construction but is still operable to establishthe high-range, neutral, and low range drive connections between theclutch output shaft 286 and the differential input shaft 306.

In operation, the vehicle 10′ can normally be operated in a two-wheelhigh-range drive mode in which the power take-off unit 18′ establishes ahigh-range drive connection between the powertrain 12 and the primarydriveline 16′ while the rear drive module 100′ is disengaged.Specifically, the range sleeve 224 and mode collar 246 respectivelyassociated with the range shift mechanism 202 and the disconnectmechanism 54′ are located as shown in FIG. 16A to establish the 2-Himode. With the mode collar 246 in its first mode position, the inputshaft 204 is disconnected from the transfer shaft 64′ such thatsubstantially all rotary power is transferred from the powertrain 12 tothe primary driveline 16′. The torque transfer device 112′ is maintainedin its first (disconnected) mode to disconnect the secondary driveline20′. While the torque transfer device 112′ is operating in itsdisconnected mode, the range sleeve 310 can be located in its high-rangeposition (FIG. 17A).

When it is desired or necessary to operate the motor vehicle 10′ in anall-wheel high-range (AWD-H) drive mode, the control system 22 can beactivated to initially signal the TTD actuator 114′ to shift the torquetransfer device 112′ into its second (connected) mode for synchronizingthe speeds of the primary driveline 16′ and the secondary driveline 20′.Upon synchronization, the controller 150 signals the actuator 56′ toshift the mode collar 246 to its second mode position while maintainingthe range sleeve in its first range position (FIG. 16B). Thisestablishes a four-wheel high-range drive connection between thepowertrain 12, the primary driveline 16′ and the input 106′ to the reardrive module 100′. In addition, the range actuator 284 can be actuatedto maintain or move the range sleeve 310 into its high-range position(FIG. 17A) such that rotary power delivered through the torque transferdevice 112′ is transmitted to the second differential 110′ at the directspeed ratio. Thereafter, the TTD actuator 114′ can be controlled to varythe torque transmitted through the torque transfer device 112′ to thesecond vehicle wheels 104L, 104R with the second differential 110′operating in an open state for permitting speed differentiation betweenthe second vehicle wheels 104L, 104R.

If during operation of the vehicle 10′ in its AWD-H drive mode, it isdesired or determined that improved traction requires operation in anall-wheel drive low-range (AWD-L) drive mode, the control system 22functions to coordinate shifting of the power take-off unit 18′ into itsfour-wheel low-range mode and the rear drive module 100′ into itslow-range mode. Specifically, the positions of the mode collar 246 andthe range sleeve 224 of the power take-off unit 18′ to establish thisconnection are shown in FIG. 16D while the position of the range sleeve310 of the rear drive module 100′ to establish this connection is shownin FIG. 17C. Thus, the low-range drive connections are established inthe power take-off unit 18′ and the rear drive module 100′. Theselow-range drive connections can be established sequentially orconcurrently based on a suitable control method and can be establishedwith the vehicle 10′ in a stationary or non-motive state.

If during operation of the vehicle 10′ in its AWD-L drive mode, it isdesired or determined that locking of the second differential 110′ wouldassist in providing even greater traction, the control system 22 canrequest operation of the vehicle in an all-wheel drive low-lock range(AWD-LOCK) drive mode. This entails signaling the range actuator 284 toshift the range sleeve 310 into its low lock position (FIG. 17D) whilemaintaining the power take-off unit 18′ in its four-wheel low-range mode(FIG. 16D).

Finally, a towing mode for the vehicle 10′ can be established byshifting the power take-off unit 18′ into its neutral mode (FIG. 16C)and shifting the rear drive module 100′ into its neutral mode (FIG.17B).

While specific aspects have been described in the specification andillustrated in the drawings, it will be understood by those skilled inthe art that various changes can be made and equivalents can besubstituted for elements and components thereof without departing fromthe scope of the present teachings, as defined in the claims.Furthermore, the mixing and matching of features, elements, componentsand/or functions between various aspects of the present teachings areexpressly contemplated herein so that one skilled in the art willappreciate from the present teachings that features, elements,components and/or functions of one aspect of the present teachings canbe incorporated into another aspect, as appropriate, unless describedotherwise above. Moreover, many modifications may be made to adapt aparticular situation, configuration, or material to the presentteachings without departing from the essential scope thereof. Therefore,it is intended that the present teachings not be limited to theparticular aspects illustrated by the drawings and described in thespecification as the best mode presently contemplated for carrying outthe present teachings, but that the scope of the present teachingsinclude many aspects and examples following within the foregoingdescription and the appended claims.

What is claimed is:
 1. A vehicle driveline comprising: an input shaftrotatable about a first axis; a range sleeve that is concentric with theinput shaft, the range sleeve being non-rotatably but slidably coupledto the input shaft and movable along the first axis between a firstrange sleeve position and a second range sleeve position; a mode sleevethat is concentric with the input shaft, the mode sleeve being slidablealong the first axis between a first mode sleeve position and a secondmode sleeve position; a planetary transmission having a planet carrier,a sun gear and a plurality of planet gears that are rotatably mounted onthe planet carrier and meshingly engaged to the sun gear; a differentialassembly having a differential case and a differential gearset, thedifferential case being coupled to the planet carrier for commonrotation about the first axis, the differential gearset being disposedin the differential case and including a pair of differential outputmembers; an axle shaft coupled for rotation with one of the differentialoutput members, the axle shaft extending through the sun gear and theinput shaft; and a power transfer unit having a PTU input and a PTUoutput, the PTU output being rotatable about a second axis that istransverse to the first axis; wherein placement of the range sleeve inthe first range sleeve position couples the planet carrier to the inputshaft for common rotation and wherein placement of the range sleeve inthe second range sleeve position couples the sun gear to the input shaftfor common rotation; wherein placement of the mode sleeve in the firstmode sleeve position when the range sleeve is in the first range sleeveposition de-couples the range sleeve from the PTU input to permitrelative rotation between the range sleeve and the PTU input, andwherein placement of the mode sleeve in the second mode sleeve positionwhen the range sleeve is in the first range sleeve position couples therange sleeve to the PTU input for common rotation.
 2. The vehicledriveline of claim 1, wherein the PTU input is rotatable about the firstaxis.
 3. The vehicle driveline of claim 1, wherein the PTU outputcomprises a bevel pinion gear that is meshingly engaged with a bevelring gear.
 4. The vehicle driveline of claim 3, wherein the bevel ringgear is rotatable about a third axis that is offset from but parallel tothe first axis.
 5. The vehicle driveline of claim 1, wherein the PTUinput comprises a first intermediate gear, and wherein the firstintermediate gear is meshed with a second intermediate gear that ismounted on an intermediate shaft.
 6. The vehicle driveline of claim 1,wherein the range sleeve comprises a first set of mode sleeve teeth anda second set of mode sleeve teeth that are spaced apart from the firstmode sleeve teeth, wherein the first set of mode teeth engage the modesleeve when the mode sleeve is in the second mode sleeve position andthe range sleeve is in the first mode sleeve position, and wherein thesecond set of mode sleeve teeth engage the mode sleeve when the modesleeve is in the second mode sleeve position and the range sleeve is inthe second range sleeve position.
 7. The vehicle driveline of claim 1,further comprising a rear drive module that is driven by the PTU output.8. The vehicle driveline of claim 7, wherein the rear drive moduleincludes a two-speed transmission, which is driven by the PTU output,and a differential mechanism that is driven by an output of thetwo-speed transmission.
 9. The vehicle driveline of claim 8, wherein therear drive module further comprises an input pinion, which is coupled tothe PTU output via a propshaft, and a clutch that selectively interruptspower transmission between a pair of rear axle shafts and the inputpinion.
 10. A vehicle driveline comprising: an input shaft that isrotatable about a first axis; a range sleeve that is concentric with theinput shaft, the range sleeve being non-rotatably but axially slidablycoupled to the input shaft; a mode sleeve that is concentric with theinput shaft; a differential assembly having a differential case and adifferential gearset, the differential case being rotatable about thefirst axis, a two-speed transmission configured to receive rotary powerfrom the range sleeve, the two-speed transmission outputting rotarypower to the differential case; and a power take-off unit having a PTUinput and a PTU output, the PTU output being disposed along a secondaxis that is not parallel to the first axis; wherein the two-speedtransmission operates in a first speed ratio when the range sleeve ispositioned in a first range sleeve position, wherein the two-speedtransmission operates in a second speed ratio when the range sleeve ispositioned in a second range sleeve position; wherein the mode sleeve ismovable between a first mode sleeve position, in which the mode sleeveis disengaged from at least one of the PTU input member and the rangesleeve, and a second mode sleeve position in which the mode sleeve islocated in a position where it is capable of transmitting rotary powerbetween the range sleeve and the PTU input member; and wherein movementof the range sleeve and the mode sleeve is coordinated to provide atwo-wheel drive high range operational mode, a four-wheel drive highrange operational mode and a four-wheel drive low range operationalmode.
 11. The vehicle driveline of claim 10, wherein the PTU input isrotatable about the first axis.
 12. The vehicle driveline of claim 10,wherein the PTU output comprises a bevel pinion gear that is meshinglyengaged with a bevel ring gear.
 13. The vehicle driveline of claim 12,wherein the bevel ring gear is rotatable about a third axis that isoffset from but parallel to the first axis.
 14. The vehicle driveline ofclaim 10, wherein the PTU input comprises a first intermediate gear, andwherein the first intermediate gear is meshed with a second intermediategear that is mounted on an intermediate shaft.
 15. The vehicle drivelineof claim 10, wherein the two-speed transmission is a planetarytransmission.
 16. The vehicle driveline of claim 10, wherein the rangesleeve provides rotary power to a first element of the two-speedtransmission when the range sleeve is in the first range sleeve positionand wherein the range sleeve provides rotary power to a second elementof the two-speed transmission when the range sleeve is in the secondrange sleeve position.
 17. The vehicle driveline of claim 10, whereinthe range sleeve comprises a first set of mode sleeve teeth and a secondset of mode sleeve teeth that are spaced apart from the first modesleeve teeth, wherein the first set of mode teeth engage the mode sleevewhen the mode sleeve is in the second mode sleeve position and the rangesleeve is in the first mode sleeve position, and wherein the second setof mode sleeve teeth engage the mode sleeve when the mode sleeve is inthe second mode sleeve position and the range sleeve is in the secondrange sleeve position.
 18. The vehicle driveline of claim 10, furthercomprising a rear drive module that is driven by the PTU output.
 19. Thevehicle driveline of claim 18, wherein the rear drive module includes atwo-speed transmission, which is driven by the PTU output, and adifferential mechanism that is driven by an output of the two-speedtransmission.
 20. The vehicle driveline of claim 19, wherein the reardrive module further comprises an input pinion, which is coupled to thePTU output via a propshaft, and a clutch that selectively interruptspower transmission between a pair of rear axle shafts and the inputpinion.